Structural elucidation studies have been successfully conducted on the alkaloidal venom of a South American ant species, Megalomyrmex leoninus, and on the probable sex pheromones of the Brown Tree Snake. New synthetic routes to a lipophilic C-terminal cysteine derivative, a set of unique tricyclic azaacetal venom alkaloids, the probable sex pheromone of the Brown Tree Snake, and a unique spiropyrrolizidine frog neurotoxin have been undertaken or completed.